Pope Benedict XVI addresses the crowd at St. Peter's Basilica in the VaticanGoogle Images

Pope Benedict XVI brought his already staunch opposition to gay marriage to a whole new level on Friday, claiming that gay people willingly ignore their God-given gender identities to pursue their sexual choices.

Sexual orientation is a choice, the pope contended, and choosing to be gay destroys the very 'essence of the human creature' in the process.

Benedict XVI made the startlingly strong attack on gay people the centerpiece of his annual Christmas address to the Vatican bureaucracy, one of his most important speeches of the year.

'People dispute the idea that they have a nature, given to them by their bodily identity, that serves as a defining element of the human being,' the pope said. 'They deny their nature and decide that it is not something previously given to them, but that they make it for themselves.'

Being gay, the pope inferred, is not something that naturally occurs, nor can it ever be called natural, so therefor to be gay is always an unnatural choice.

'The manipulation of nature, which we deplore today where our environment is concerned, now becomes man's fundamental choice where he himself is concerned,' he said, underlining the idea that being gay manipulates nature.

Alarmed by the gains that same-sex marriage has made in the U.S. and Europe in recent months, the pope hopes his increasingly hard hitting speeches will blunt efforts to legalize gay marriage in France and Britain.

According to the Huffington Post, to bolster his case Benedict quoted the chief rabbi of France, Gilles Bernheim, who has claimed that legally permitting gays to marry and adopt children was an invisible 'attack' on the traditional family made up of a father, mother and children. Gay couples should never be allowed to marry or raise children of their own, the pope inferred.

The pope has been remarkably vocal on gay issues in recent weeks. Earlier this week, in his annual peace message, Benedict said that gay marriage, like abortion and euthanasia, was a threat to world peace.

Responding to the pope's comments Italy's main gay rights group Arcigay said the pontiff’s claims were 'absurd, dangerous and totally out of synch with reality.' Four progressive U.S. Catholic organizations representing gay, lesbian and transgender people said the pope had an 'outmoded' view of what it means to be man and woman.

'Catholics, following their own well-formed consciences, are voting to support equal rights for LGBT people because in their churches and communities they see a far healthier, godly and realistic vision of the human family than the one offered by the pope,' according to a statement from the groups Call To Action, DignityUSA, Fortunate Families, and New Ways Ministry.

For the Vatican the gay marriage issue now goes well beyond questions of homosexuality, threatening what the church considers to be foundational: a family based on a man, woman and their children - and also the church's role in their lives.

Speaking to the Vatican bureaucracy the pope added that rejecting nature is at the root of the 'choice' to become gay. To embrace being gay is to reject one's true nature. 'Man and woman as created realities, as the nature of the human being, no longer exist. Man calls his own nature into question. From now on he is merely spirit and will.'

The Vatican's heightened offensive on international gay equality has won few new hearers, however. In addition to the recent historic U.S. election gains, the Constitutional Court in predominantly Catholic Spain upheld the law legalizing gay marriage last month.

Earlier this month, the conservative British government announced plans to introduce a bill next year legalizing gay marriage, though it would ban the Church of England from conducting same-sex ceremonies.

In France, President Francois Hollande has said he would enact his 'marriage for everyone' plan within a year of taking office last May. The text will go to parliament next month.

Meanwhile last week the pope met with and blessed Rebecca Kadaga, the Speaker of the Uganda Parliament who has promised to pass the draconian 'Kill The Gays' bill as a 'Christmas gift' to Uganda’s Christians.

The bill, which has prompted an international outcry, proposes the death penalty whenever HIV is knowingly or unknowingly spread from one to another consenting adult; it proposes a seven-year prison sentence for consenting adults who have gay sex, life sentences for people in same-sex marriages and jail terms for anyone who doesn't immediately report a gay or lesbian person to the authorities.